In the operation of electronic equipment, it is necessary to shield against electromagnetic emissions. One such source of emissions is the face of a cathode ray tube (CRT), particularly that employed in a color monitor.
A presently used shielding arrangement uses a filter window permanently adhered to a plastic bezel and positioned adjacent the tube face. The window is comprised of a pair of coextensive curved glass plates having a fine copper mesh laminated therebetween. The mesh protrudes from the plates on all sides thereof, forming a sleeve, the extremity of which is wrapped about a core of insulative material to form a ring-like resilient member. Shielding is effected by clamping the last mentioned member to the metal chassis housing the electronics for the CRT. Clamping has been accomplished through the use of flat metal plates and a relative large number of associated screws for compressing the member.
A number of problems are present in the foregoing shielding arrangement, particularly as to shielding integrity and cost of manufacture. For example, removal of the member for the purpose of servicing the electronics in the chassis may result in unacceptable emissions when the seal is reestablished. Also, since the bezel is permanently affixed to the glass filter, the entire bezel assembly must be discarded. The same is true if the glass filter is cracked. As to cost, the preparation of the bezel assembly, preferably by the glass filter manufacturer, results in increased manufacturing and shipping costs. Moreover, the implementation of the EMI/RFI seal by installation of the large number of screws in the compression plates, results in increased assembly time.
What is desired is a shielding arrangement in which: the bezel and glass filter are separate entities, capable of being easily assembled and disassembled; the assembly time is reduced through the elimination of the compression plates and screw fasteners; and most significantly, the reproducibility factor with respect to EMI/RFI integrity is greatly increased. The assembly of the present invention fills such a need.